For many multimedia applications, not only is processor speed important, but also input/output bandwidth is a critical factor that limits applications on personal computers. To address this limitation, the IEEE 1394 standard enables high-performance multimedia connections with camcorders, televisions, stereos, CD changers, set-top boxes, mixing consoles and music keyboards, as well as traditional personal computer devices. Also known as the "FireWire" standard, IEEE 1394 provides a bus interface standard for portable and desktop computing environments. The IEEE 1394 Standard serves as an important linking technology that bridges the consumer and computer markets and describes a serial bus driven by an advanced communication protocol. The IEEE 1394 serial bus is designed for low system cost, while providing the data transfer rates needed for high-performance peripheral buses.
Developed by the Institute of Electrical and Electronics Engineers (IEEE) and its list of member computer companies, the IEEE 1394 standard is a serial bus interface that enables low-cost, high-speed digital data transfer and communication. Transfer speeds between devices can reach up to 400 megabits per second (mbps) via both asynchronous and isochronous data transfer modes. The IEEE 1394 Standard interface lends itself to video applications because it operates an isochronous time-slice system. For example, if the system was configured to output one frame per 1/15 seconds, at least one frame will exist in every packet that is sent out. This results in smooth looking video. For that reason, the IEEE 1394 Standard interface is highly compatible with technologies like asynchronous transfer mode (ATM) which also operates in an isochronous mode.
Benefits of the IEEE 1394 Standard are a real-time transmission of data that provides the benefit of an ideal interconnect for multimedia applications. Using a small, durable and flexible cable and cable connectors, the IEEE 1394 Standard generates cost savings and eliminates certain cable requirements. The IEEE 1394 Standard provides universal input/output interconnects that integrate input/output ports while consolidating printed circuit board space. Moreover, the IEEE 1394 Standard provides peer-to-peer communication structure that permits peripherals to communicate directly with each other without burdening the host unit.
The IEEE 1394 Standard provides a high speed serial bus that uses packetized data that includes a header. The header includes routing information. In addition, the packetized data includes payload data. Physical characteristics of the media are not necessarily designed for a long transmission distance. The IEEE 1394 Standard is designed for short distances such as local area networks that operate on a desktop bus. The distances are often longer than simply the desktop, but the IEEE 1394 Standard is not intended to be used for local area network operations. In essence, therefore, the IEEE 1394 Standard provides a high speed interconnect to replace serial buses and parallel buses for accessing devices such as workstations, home computers, televisions, VCRs, and camcorders with various media types such as audio, video and text.
Known IEEE 1394 standard bus interface devices do not provide a practical way to specify the bits via a select number of bits in the address field. For example, there is no practical way with known IEEE 1394 standard methods and systems to precisely specify which bits are to be written to. Existing systems write via the IEEE 1394 Standard with one word or access that writes to all four bits at the same time. If there are independent functions for various ones of the bits, there is no known way to control only the bits of interest by a given write access without affecting other bits. With existing interface devices, there is no way to assure that if four bits are to be written simultaneously, that the software does not require keeping an image of the output register. Thus, when there is the need to modify only one bit, existing systems must either read the output, as with a read-modify-write operation, or these systems must change an internal copy of the output and then re-output the changed output.
With the existing interface devices, there is no way to control only affected bits without writing an image of the entire output register in memory or conducting a read-modify-write operation. Moreover, there is no way to effectively control only the bits of interest without performing an independent write to the different bits. Address synchronization issues also arise with regard to different processes that generate the various inputs end outputs and, as a result, there is no effective way to address synchronization issues or even separate synchronization issues from hardware issues. Finally, known interface devices often employ an "atomic operation" that locks the IEEE 1394 Standard bus during the read-modify-write cycle. This time consuming process slows down data transfer. Thus, a process that eliminates this atomic operation would increase the input/output speed to the communication according to the IEEE 1394 Standard.